A novel approach of Moving Target Detection (MTD) based on sub-apertures for the single-channel SAR is proposed in this paper. Firstly, the differences between the images of moving targets and stationary targets in sub-apertures are analyzed. The image subtraction between two sub-aperture images for clutter removing is proposed. Secondly, the principle and process of how to gain the sub-apertures and the match of their images are presented. The process flow of MTD and locating is designed. Lastly, the details about how to do target locating are described, combined with the length of range migration. The approach is validated by simulated echo data. This approach has several advantages, only single channel antenna, low cost, less computation load, real-time data processing, etc.